Centralized traffic controlling system for railroads



Julyze, 193s.

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS BUS.

ConTrol OTce D. F. DE LONG Filed Sept. ll, 1935 FIG.. LA.

6 Sheets-Sheet 2 July 26, 1938. D. F. DE LONG CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed sept. 11, 1935 6 Sheets-Sheet 3 July 26, 1938. D. F. DE LQNG' l 2,124,846

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS 'Fired sept. 11, 1935 e 'sheets-sheet 4 com l rl N v Nah. +V.) r1.6

MIF

July 26,1938.

D,` F, DE LONG 73,124,846

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS 6 Sheets-Sheet 5 Filed Sept. ll, 1955 M n R o Mm V A u W d Ike?. um t. u u Lrg. 1:\ au

c o ...f8.5 L Summum July 26, 1938. D. F. DE LONG CENTRALIZED TRAFFIC CONTROLLINGv SYSTEM FOR RAILROADS Fivled Sep'fw, l1, 1935 6 Sheets-Sheet 6 ATTORNEY wmv :o tn Panneau@ Patented July 26, 1938 CENTRALIZED TRAFFIO CONTROLLING SYS- TEM FOR RAILROADS Darrol F. De Long, Rochester, N. Y., assignor to General Railway Signal Company, Rochester, N. Y.

Application September 11, 1935, Serial No. 40,114

9 Claims. (Cl. 177-353) This invention relates to centralized traffic controlling systems for railroads, and it more particularly pertains to the communication part of such systems.

By means of the centralized traflic controlling system contemplated by the present invention, a central control ofce is placed in communication with a number of outlying field stations in such a way that controls may be transmitted to these field stations for governing the operation of traino controlling devices located at the various stations. Likewise, the conditions of the various traic controlling devices at each station are transmitted from each station to the control ofi-ice to advise the operator of the location of trains and the condition of the traffic controlling devices, such conditions being transmitted as indications.

The present invention more particularly relates to a centralized trailc controlling system wherein the supervision of the traiiic governing devices and the indication of their conditions are accomplished over a communication system comprising two line circuits, namely, a control line circuit and an indication line circuit. The present invention is more particularly directed to a trafc controlling system in which a repeater station is provided when the distance between cer-tain of the eld stations and the control office is `such that it is impractical to transmit impulses between the control oflice and these certain field stations without the use of undesirably high line voltages and/or unduly large line conductors, because of the length of the line circuits.

An important feature of the present invention is a storage and repeater arrangement, whereby it is possible to store indications from a distant station in the repeater station during one halfstep of the stepping mechanisms and repeat the stored indications from the repeater station to the oice during the next half-step. of the stepping mechanisms.

In accordance with another feature of the present invention it is possible to operate one or more laterals or branches extending from the main line of the communication system without the necessity of looping the line circuits of such laterals in series with the main lline circuit, with the consequent need of high voltage and/or large line conductors. It will be obvious from the Ydescription which follows that the .repeater station as disclosed in the present invention may be installed at the locations where such laterals .branch off from the main line, irrespective of whether this branch is made at the end of the main line or at some location between the oice and the end of the line. It will also be obvious that laterals may be branched oi the above mentioned laterals by means of the repeater arrangement disclosed, all within the scope of the present invention.

Another object of the present invention is the provision of a repeating circuit so arranged that the system will operate at its desired speed without the need of increasing the size of the line conductors or providing line voltages beyond a reasonable value. As a result of the repeating arf rangement provided in the present invention, installation costs of a centralized trailic controlling system are reduced because it is possibleV to keep the size of the line battery and the line conductors down to a minimum. In other words the present circuit arrangement is so arranged that when the economical limit of line wire size is reached and the economical limit of battery size is reached, the line circuit will be arranged to repeat into another line circuit for the transmission of controls and indications, with this process repeated asvoften as required.

Another object of the present invention is the provision of a circuit arrangement for directly repeating impulses from a primary control line circuit in straight time cascade into asecondary control line circuitf Y YAnother object of the present invention is the .provision of a storage arrangement in the repeater station whereby indications transmitted from a distant eld station during a particular cycle of `operations leave the field stations on one half-step of the stepping mechanism and 4arrive at the control oice on the following half-step when only Yone repeater station *is employed. When two repeater stations are employed, indications transmitted from a eld station beyond the second repeater station leave such field station on one half-step of the stepping mechanism and arrive at the control office on the second half-step following. This arrangement of storage and repeater station is so organized that irrespective of the number of` repeater stations employed, the length of the operating cycle for anygiven capacity remains the same, or in other words, the'number of steps necessary for the stepping mechanisms for the control oice and Athe Iield stations between the control office and the rst repeater station remain the same irrespective of Athe use of one or more repeater stations.

Other objectsVpurposes and characteristic features of the present invention will bein partpobvious `from the accompanying drawings and in part pointed out as the description of the invention progresses.

The system of the present invention is an improvement over the repeater system disclosed in the prior application of W. D. Halles, Ser. No. 33,826, led July 30, 1935, Patent No. 2,097,789 dated November 2, 1937.

In describing the invention in detail reference will be made to the accompanying drawings, in which like reference characters designate corresponding parts, in which distinctive exponents are used at different locations and in which:

Fig. 1 is a diagrammatic illustration of the layout of a system to which the present invention is particularly applicable.

Figs. lA and 1B illustrate in a diagrammatic and conventional manner the circuit arrangement at the control ofiice end of the communication system.

Fig. 2 illustrates in a diagrammatic and conventional manner the circuit arrangement at a iield station located between the control office and the repeater station.

Fig. 3 illustrates in a diagrammatic and conventional manner the circuit organization at the repeater station.

Fig. 4 illustrates in a diagrammatic and conventional manner the circuit arrangement of a eld station located beyond the repeater station.

Fig. 5 is a typical indication code table which will be used in explaining the operation of the present system. f

In following the circuits of the present invention Figs. 1A, 1B, 2, 3 and 4 should be placed together in the order named with correspondingly identified lines in alignment.

For the purpose of simplifying the illustrations and facilitating in the explanation, the various parts and circuits constituting the embodiment of the invention have been shown diagrammatically and certain conventional illustrations have been employed, the drawings having been made more with the purpose of making it easier to understand the processes and mode of operation than with the idea of illustrating the specic construction and arrangement of parts that would be employed in practice. Thus the various relays and their contacts are illustrated in a conventional manner and symbols are used to indicate connections to the terminals of batteries or other sources of electric current instead of showing all of the wiring connections to these terminals.

The symbols (-1-) and are employed to indicate the positive and negative terminals respectively of suitable batteries or other sources oi.' current and the circuits with which these symbols are used always have current iiowing in the same direction, that is from (-1-) to The symbols (B+) and (B-) are employed to indicate the positive and negative terminals respectively of a battery or other source of direct current having a mid-tap (CN) and the circuits with .which these symbols are used may have current ilowing in one direction or another depending upon whether the circuit is connected to (B+) or (B).

In the lower right hand portion of Fig. 1B relay FC is blocked in, in dotted lines. This is the same FC relay which is illustrated in the upper portion of Fig. 1A and in order to simplify the circuit connections from contact 9| of relay 2SA `through contact 99 of relay FC to contact 92 of relay ZFP, the location of relay FC has been indicated in two places. It is believed however that this will not be confusing in following the operation of the system especially since the operating and stick circuits of the FC relay are not shown in the present disclosure.

Control oce equipment-The control orce equipment includes a neutral line relay F which repeats the impulses applied to the control linecircuit, comprising control line conductor CL and control return conductor CR, from battery CB'. Neutral line repeating relays FP and ZFP repeat the impulses applied to relay F and since these relays are of the quick acting type they follow the operations of relay F with minimum delay. Slow acting line repeating relays SA and 2SA are for the purpose of defining the bounds of each operating cycle, that is these relays are picked up at the beginning of each cycle, remain up throughout the impulsing of the cycle and are dropped at the end of the cycle.

Cycle determining relay C and code determining relay CD are picked up in response to thev actuation of button SB at the beginning of a.l cycle, during which controls are transmitted. The detailed circuits for controlling the operation of relays C and CD are not shown since they are immaterial for an understanding of the present 'invention and may be arranged as shown in detail in the prior patent to T. J. Judge and C. S. Bushnell Patent No. 2,082,544 dated June 1, 1937.

Field cycle determining relay FC remains down during a control cycle but is picked up during a duplex cycle or a cycle for the transmission of indications alone. The circuit arrangement of relay FC is likewise omitted from the present drawings for the sake of simplicity, but this relay may be controlled in the same manner as disclosed in the above mentioned application Ser. No. 640,062.

Code sending relays PC and NC are for the purpose of applying (-1-) and impulses respectively to the control line circuit during a cycle of operations. Relays MB and MF are for the pur-- pose of receiving indications during an operating cycle over the primary indication line circuit, comprising indication line conductor IL and indication return conductor IR.

A suitable step-by-step relay bank is employed including relays VP, IV, 2V and LV. Relay IV, 2V and LV pick up during the de-energized or off periods of theimpulses in the control line circuit and relay VP shifts its position during the energized or on periods of the impulses in the control line circuit. When the stepping relays are picked up they are stuck up until the end of the cycle. Half step relay VP is picked up and dropped during alternate on periods of the cycle, all of which will be pointed out in detail. Control line impulsing relay E controls the application of the impulses to the primary control line circuit by opening and closing the energizing circuit of the PC and NC relays at the proper times as determined by the response of the stepping relay bank in the control office to the impulses applied to the line.

Resistance CRS is a charging resistance for `precliarging the indication line circuit extending `from the oflice to the repeater station, to apply a charging current at the beginning of each interval devoted to the transmission of indications.

Although not shown in the present drawings, it will be understood that the control oilice is provided with a suitable control machine which includes a miniature track diagram representative of the actual track layout in the eld. Certain control levers and buttons which are manually operable to obtain the desired control are included in the control machine, switch machine lever SML and starting button SB being typical of such devices. It Willbe understood that a starting button is provided for each group of control levers and is associated with a particular field station, so that the positioning of the control levers for a particular station results in the transmission of controls to that station following the operation of the associated starting button. Station selection is provided by the particular CD relay which is picked up in response to the operation of a particular starting button, by connecting the PC and NC relays to the channel circuits selected by the stepping relay bank by means of code jumpers connected in various combinations for providing station selecting codes.

For the purpose of illustrating how the reception of indications on the MB and MF relays in the control office store these indications for the purpose of station registration and indicating registration, pilot relays IPB, IPF and ZPB are shown in Fig. lA. Station relays IST and 5ST are illustrated as being typical of the registration of a transmitting iield station in the control office by the'selection and operation of one of these station relays during a cycle of operations. Indication storing relay IRF is illustrated to show how an indication received from station No. 5 is transferred from the message receiving relay MIF during a cycle of operations when station No. 5 isselected. Relay IRF is of the polar magnetic stick type, that is its contacts are operated to the right and left when (B-) and (B-|-) respectively are connected to its winding by way of contact 96 of relay MF. It will be understood that there are other indication storing relays for receiving other indications from station No. 5 and from other stations in the system, but itis believed that the illustration of relay IRF and an explanation of its operation will be suicient for an understanding ofthe present invention.

Repeater station equipment-It is assumed (see Fig. 1) that the present system comprises a control ofiice connected to a repeater station by means of primary control and indication line circuits and that there are four field stations connected to these line circuits between the control oiiice and the repeater station. It is also assumed that there are four field stations connected to the secondary control and indication line circuits which extend beyond the repeater station.

The repeater station (illustrated in Fig. 3) includes a biased to neutral polar line relay F3 and a neutral quick acting line relay IFS. These line relays repeat the impulses applied to the primary control line circuit in the control ofce. The (-1-) and impulses applied to the primary control line circuit and received by relay F3 effect the operation of relays FC3 and NC3 respectively to apply corresponding polar impulses to the secondary control line circuit, comprising control line conductor CL1 and control return conductor CR1 extending to the eld stations beyond the repeater station. The impulses in the primary control line circuit and the impulses repeated into the secondary control line circuit are repeated (irrespective of their polarity) by neutral line relays IF3 and FN3 respectively.

Slow acting relays S3, SA3 and SB3 are for the purpose of marking the bounds of cycles of operation, the detailed operation of these relays being explained later.

Relays FP3 and 2FP3 operate during a cycleffor the repeating of indications, these relays repeating the operations of line relay FN3 as will be described in detail. Lock-out relay LO3 functions to provide a lock-out operation so that field stations located in the primary section of the communication system may obtain access to the primary line circuits for the purpose of transmitting their indications in preference to the repeater station. 'I'he detailed lock-out feature will be described later.

Resistance CRS3 corresponds to resistance CRS in the control oice andis for a similar purpose, that is the. secondary indication line circuit is precharged over a circuit including this resistor to apply a charging current at the beginning of each interval devoted to the transmission of indications. Indication battery IB(1 corresponds to indication battery IB in the control oiiice and it will be understood that these batteries are for the purpose of energizing the secondary and primary indication line circuits respectively for the transmission of indications. Relays MB3 and MP3 correspond to relays MB and MIF in the control oiiiceand are for the=pur pose of receiving indications transmitted from a field station in the secondary section. These indication receiving relays receive the registration and indication codes transmitted from a iield station in the secondary section during one half step of an operating cycle and transmit the corresponding codes to the control oice during a following half-step of an operating cycle.

Resistance I R3 is a compensating resistance for compensating for the lower winding of relay LO=3 which is removed from the primary indication line circuit after the lock-out period of a cycle. Resistance 2R3 is a compensating resistance to compensate for the value of resistance of the primary indication line circuit which is disconnected when the repeater station is transmitting. It will be understood that when the repeater station is located at the end of the primary section, as illustrated in Fig, 1, resistance 2R3 is not required and the terminals to which it is connected are strapped by a jumper and the i resistance removed. On the other hand, if the repeater station is located at a point in the primary section With field stations connected farther out from the control office, then resistance 2R3 is provided, the value of which is determined by the resistance of the indication line circuit which is disconnected when the repeater station is transmitting.

Field station equipment-A field station (see Fig. 2) located in the primary section is similar to a field station (see Fig. 4) located in the secondary section. Therefore the circuit arrangement of Fig. 2 is the same as the circuit arrangement of Fig. 4 except that reference characters are provided in accordance with the figure number and adiilerent connection of the station identifying code jumpers is-provided at each station. These field stations each include a biased-to-neutral polar line relay F and line repeating relays FP, SA and SB (with distinctive exponents), which relays operate in a similar manner to corresponding `relays in the control oiiice, except that the line relay is a polar relay for receiving the polar impulses in the control line circuit. Relay SB (with distinctive exponent) corresponds to relay 2SA in the control oilice except, as indicated in the field station drawings, this relay is not of the slow acting type.

Each field stationincludes a bank ofv stepping relaysvIV.. 2V, LV, and the associated half step relay VP, (with distinctive exponents) operating substantially in synchronism with corresponding relays in the control oice, in response to impulses applied to the control line circuits. The detailed circuit arrangement for operating the stepping relay banks and the line repeater relays have not been shown since they may be the saine as for corresponding relays in the control oflice. It is thus believed obvious that the line repeating relays and the stepping relays operate in response to the operations of relays FP2 and F124 by means of circuits which are not shown but merely indicated by dotted line connections 265 and 465.

Relays PB and PF (with distinctive exponents) are controlled locally in accordance with the local jumper connections and the positions of local relay contacts. YThese relays function to condition the indication line circuits in accordance with indications to be transmitted during the different periods of a cycle as will be pointed out in detail.

Lock-out relays L02 and L04 are picked up in response to a eld start condition at the associated station and they function to close the primary indication line circuit or the secondary indication line circuit respectively, for initiating a cycle of operations for the transmission of indications from the associated station. It will be understood that lock-out relay L02 locks out more distant eld stations in the primary section and lock-out relay L04 locks out more distant field stations in the secondary section, so that these more distant stations are ineffective to obtain access to the communication system during a cycle of operations for the transmission of their indications when the illustrated stations have use of the line circuits.

Resistance units IR2 and IR4 are compensating resistances for compensating for the resistance of the lower winding of the associated L0 relay which is removed from the indication line circuit after the lock-out period. Resistance -units 2R2 and 2R4 are compensating resistances to compensate for the value of resistance in the associated indication line circuit which is disconnected when a particular eld station is transmitting. When the iield station of Fig. 2 is transmitting, primary indication line conductor IL is connected to return line conductor IR by way of resistance 2R21, which resistance is of the proper value to compensate for the resistance of the primary indication line circuit which would be completed at the end station of a series of eld stations connected to the primary indication line circuit. Likewise, when the eld station of Fig. 4 is transmitting, the secondary indication line conductor IL1 is connected to return conductor IR1 by Way of resistance 2R4, which resistance is of the proper value to compensate for the resistance of the secondary indication line circuit which would be completed at the end station of a series of eld stations connected to the secondary indication line circuit.

Track switches TS2 and T84 are illustrated as being controlled by switch machines SM2 and SM4 in response to the operation of switch machine relays SMR2 and SMRA. VThe occupied and unoccupied conditions of the illustrated track sections are repeated by track relays T2 and 'I'4 in the usual manner.

The control of the signals 'at the illustrated stations has not been shown, since the control of the switch machine may be considered typical of the manner in which additional steps of the cycle function to control signals in response to additional impulses. Change relays CH2 and CH4 are normally energized and are dropped (circuits not shown) in response to a change in condition at the associated eld station, for initiating the system into a cycle of operations for the transmission of indications.

The station selection portion of the system is not illustrated since this feature is immaterial for an understanding of the present invention. Station selection may be provided as explained in detail in above mentionedv Patent No. 2,082,544. It need only be mentioned here that station relays S02 and S04 are picked up at the beginning of a control or duplex cycle and remain up after the station selection steps of a cycle at the associated station only when controls are to be transmitted to this associated station.

General operation For convenience in describing the operation of this system the control line circuit and the indication line circuit (see Fig. 1) extending from the control oice to the repeater station will be referred to as the primary control line circuit and the primary indication line circuit respectively. The control line circuit and the indication line circuit extending from the repeater station to the distant eld stations will be referred to as the secondary control line circuit and the secondary indication line circuit respectively. It will be understood that the number of field stations included in the primary and secondary line circuits may be varied to suit operating conditions but the arrangement illustrated in Fig. l is typical.

The repeater station of the present invention repeats or retransmits the controls to the secondary section in straight time cascade, while the indications from the secondary section are transmitted to the repeater station on one half-step of a cycle of operations and then repeated or retransmitted to the control office on the following half-step. In other words an indication from any iield station in the secondary section leaves the transmitting field station on one half-step and arrives at the control oiice on the following half-step.

From the above it will be obvious that a iield station in the secondary section cannot register a pulse in the control ofce during the i'lrst off period or iirst half-stepof a cycle. It will be pointed out during the detailed description of the operation of the.4 system that practical use is made of this inability to transmit from the secondary section into the control oilice during the rst off period, so that no loss of station or indication capacity will result for those stations connected to the secondary section, by deliberately assigning the station registration codes for all stations in the secondary section to start 01T with a non-pulse on the iirst half-step.

As noted in Fig. 1, and for convenience in describing the operation of the system, a digit of a code is one which impulses or closes the indication line circuit, While a digit of a code is a non-pulse or one which leaves the indication line circuit open. It will be observed that the rst code digit of all the stations in the secondary section begin with In accordance with the above discussion and as will be later pointed out, it will be apparent that this digit (non-pulse) eiects the registration of this digit for stations in the secondary section during the first off period without the actual transmission of any code digit from the repeater station to the control office.

In the event that any one of the field stations connected to the secondary line circuit (secondary section of Fig. 1) has new indicationsto transmit to the control office, the transmitting eld station transmits these indications to the repeater station where they are received on the MB3 and MF3 relays during one half-step of the operating cycle and retransmitted to the control oifice in accordance with the condition kof the MB3 and MF3 relays during a succeeding half-step oi" the cycle.

The 1ockout feature at the repeater station functions the same as at an ordinary field station. The repeater station is inferior to all stations connected to theprimary line circuit (primary section of Fig. 1), which are located nearer the control office, and the repeater` station is superior to all eld stations more distant from the control ofce. The lock-out feature at the eld stations is of the geographic lock-out type, that is a eld station in the secondary section nearer the repeater rstation is superior to more distant field stations connected to the secondary line circuits and a eld station in the primary section nearer the control oiice is superior to vmore distant stations -in that section.

One or more repeater stations may be used as required and if more than one repeater station is used in the system the controls are repeated inthe same manner as illustrated in the accompanying drawings Without any storage feature, While the indications are first received at the repeater station associated with the line section to which the transmitting eld station is connected during one half-step of the stepping mechanisms associated with this section, with the received indications retransmitted from the repeater station into the .next section during a following half-step of the stepping mechanisms and this is repeated as Ymany times as there lare repeater stations in the system.

The line circuits of a selector system such as disclosed in the above mentioned Patent No. 2,682,544 comprise a control line circuit, including control line conductor CL control return conductor CR, and an indication line circuit including indication line conductor IL and indication return conductor IR. VThese two line circuits correspond to the control line circuit, including conductors l and i2, and the indication line circuit including conductors l 4 and l5 of the above mentioned prior application. In a system of this character the control line conductor CL is connected .to the control return conductor CR at the repeater station associated with the primary line circuit, with the line relays of any field station` Orstations between the repeater station and the control cnice, as well as the line relay at the control oiice and at the repeater station connected in series with the primary control line wire.

The primary control Yline circuit is energized with positive and negative impulses from a control line battery in the control oice for the purpose of transmitting controls and `for the purpose of causing the synchronous step-bystep operation at the control cnice and at the primary stations, as will be later explained.

The primary indication line circuit is ,energized from an indication line battery in thecontrol oilice, having included therein at the control office, message receiving relays MF and MB which are controlled through front and yback contacts respectively of relays FP and 2F13, as well asA through contacts of relays PC and NC, .to include these message receiving relays in thel indication line circuit at the properintervals of the operating cycle. The primary indication line `conductor extends to all of the eld stations connected to the primary line circuits and normally includes a back contact, such as back contact 256 of relay LO2 of Fig. 2, at any station located between the oi'lice and the repeater station. In the present embodiment the primaryindication line conductor terminates at front Contact of relay LO3 at the repeater station.

When a particular eld station is transmitting, the look-out relay at that station vis picked up thereby rendering the open or closed conductive condition ,or the primary indication line circuit with which the transmitting station is associated dependent upon the control of either a relay similar to relay PF2 or FB2 of Fig. 2 in accordance withkwhether the primary control line circuit is energized or cle-energized. It will be understood hat the above discussion assumes that the transmitting eld station is connected to the line circuits associated with the primary section.

A similar condition exists with regard to the secondary section, that is the secondary control line circuit includes line relays at the field stations of this section, with the secondary control line conductor CL1 permanently connected to the secondary return lline conductor CB1 at the end station. The lock-out arrangement and the conditioning of the secondary indication line circuit .by the PB4 and PF4 relays associated with the secondary indication line circuit is similar to the operation of corresponding relays associated with the primary indication line circuit, with the secondary indication line circuitl normally open at the last station.

Detailed operation Normal conditions-With the system in its normal condition as indicated in the accompanying drawings, the primary control line circuit and the secondary control line circuit are both deenergized. The primary indication line circuit and the secondaryindicationline circuit are both normally open. All relays in the control oflice and at the lrepeater station are normally de-energized. .All relays at the eld stations (Figs. 2 and 4) are likewise normally de-energized, with the exception `of the track relays T2 and T4 which are illustrated in their picked up conditions since it is assumed that the associated track sections are unoccupied. Change relays CI-I2 and CI-I4 are normally energized and are likewise shown in .their picked up conditions since it is assumed that no eld start has been initiated.

For convenience in describing the operations which follow, the energized or impulse periods of the control line circuits will be referred to as f on periods, while the de-energized periods between impulses Will be referred to as off periods. The system will be described as stepping through cycles each comprising a conditioning on period, a first ofi period, a first on period, a second.oi period, a second on period and a third (clearing out) oifperiod vThese ve distin'ctive periods (exclusive of the clearing out period), of an operating cycle are illustrated in the code tablepf Fig. 5 and will be referred to later in describing the transmission of codes from stations-in the-primary and secondarysections.

lJlfamtal start-It will rst be assumed that the operator in the control oiiice desires to move track switch T84 at the field station illustrated in Fig.; llirom'its normal locked position to its reverse locked position. It willbe assumed that therillustrated eld station responds lto a code combination of (-1-) and Onthe lrst two steps of the operating cycle. It will also be assumed that the track switch is operated to its reverse position in response to a impulse on the third step of the cycle.

With the system in its normal condition the actuation of starting button SB in the control ofce is eiective to pick up relays C and CD for initiating a control cycle. Since the detailed circuit arrangement for controlling the C and CD relays is immaterial for an understanding of the present invention it has been omitted from thepresent disclosure, but this circuit arrangement may be the same as disclosed in the above mentioned application Ser. No. 640,062. It will be understood that only one CD relay can be picked up at any one time and only at the time the system is in its normal condition.

The picking up of relays CD and C closes a circuit for picking up relay PC which extends from (-1-), (Figs. 1A and 1B) back contact 38 of relay E, conductor I0, front contact 4| of relay C back contacts 43 and 44 of relays 2V and |V respectively, conductor 45, front contact 46 of relay CD, code jumper 5, PC bus 41 and winding of relay PC to 11n/pulsing and stepping operations- The picking up of relay PC energizes the primary control line circuit with a (1) impulse to mark the beginning of the conditioning on period. this impulse circuit extends from the (-1-) terminal of battery CB, front contact 5| of relay PC, back contact 54 of relay NC, winding of relay F, primary control line conductor CL, winding of relay F2, primary control line conductor CL, windings of relays F3 and |F3, primary control return conductor CR, back contact 50 of relay NC and front contact 53 of relay PC to the terminal of battery CB.

This energization of the primary control line lcircuit picks up relay F in the control oice and positions the polar contacts of relay F2 (and similar line relays at any other stations connected to the primary control line circuit) to the right. Relay F3 at the repeater station likewise positions its polar contact 381 to the right and relay IF3 is picked up. Relay F closes an obvious circuit at its front Contact 61 for picking up relay FP, relay FP closes an obvious circuit at its front contact 68 for picking up relay EFP, relay l2FP closes an obvious circuit at its front contact 69 for picking up relay SA and relay SA closes an obvious circuit at its front contact 10 for picking up relay 2SA.

Relay F2 closes an obvious circuit at contact 261 in its right hand dotted position for picking up relay FP2. The following impulses which are applied to the control line circuit effect the intermittent operation of relays F2 and FP2 which, by means of circuits not shown in Fig. 2, control the operations of the relays SA2, SB2, VP2, |V2, 2V2 and LV2, but since these operations are similar to corresponding operations at the eld station of Fig. 4, which will be pointed out later, it is believed unnecessary to complicate the disclosure by including the detailed circuits of the above mentioned relays at the primary station (Fig. 2).

Relay F3 closes an obvious pick-'up circuit for relay PC3 at contact 361 in its right hand dotted position. Relay PC3 closes an obvious circuit at its front contact 366 for picking up relay S3 and Relay S3 closes a circuit for picking up relay SB3, which extends from (1), front contact 310 of relay S3, back contact 38| of relay LO3 and Winding of relay SB3 to The picking up of relay PC3 applies a (-1-) impulse to the secondary control line circuit over a circuit extending from the (-1-) terminal of battery CB1, front contact of relay P03, back contact 354 of relay NC3, winding of relay FN3, secondary control line conductor CL1 (and including other line relays at any other stations connected to the secondary control line circuit) Winding of relay F4, secondary control return 'conductor CRl, back contact 350 of relay NC3 and front contact 353 of relay PC3 to the terminal of battery CB1.

Relay FN3 is picked up in response to the energization of the secondary control line circuit and relay F4 actuates its polar contacts to the i right. It will be understood that the line relays at the field stations interposed between the repeater station and the field station of Fig. 4 operate in response to the impulses applied to the secondary control line circuit, but since it is believed unnecessary to show the circuits of these stations, only brief mention will be made of their operation later in the description.

At the eld station of Fig. 4 the actuation of Contact 451 of relay F4 to the right closes an obvious pick-up circuit for relay FP4. Although the detailed circuits are not shown in Fig. 4, in accordance with the operation of the system, disclosed in the above mentioned application Ser. N0, 640,062, the conditioning (-1-) impulse applied to the secondary control line effects the pick-up of the station relays at a portion of the eld stations, such as relays S04 of Fig. 4. Thus, due to the actuation of contact 4|4 of relay F4 to the right it will be assumed that relay SO4 is picked up and remains in its picked up condition in response to the station selecting impulses applied to the line circuits for selecting the station illustrated in Fig. 4, so that the first control impulse following station selection will be eiTective at the station illustrated in Fig. 4, due to closed front contact 4|5 of relay S04.

As above mentioned, the detailed circuits for controlling relays SA4, S134, VP4, |V4, 2V4 and LV4 at the field station illustrated in Fig. 4 have been omitted since this control may be effected in the same manner disclosed in the above mentioned application Ser. No. 640,062 and indicated by dotted line 465.

The energization of the primary and secondary control line circuits as above described is effective to provide the conditioning on period of the cycle. During this on period, relay VP in the control oice is picked up over a circuit eX- tending from (1-), front contact 1| of relay SA, front contact 12 of relay 2FP, conductor i2, back contacts 85 and 13 of relays 2V and iV respectively and winding of relay VP to Relay VP closes a rst stick circuit for itself extending from (-1-), front contact 1| of relay SA, conductor front contact 14 of relay VP, back contacts 85 and 13 of relays 2V and IV respectively and winding of relay VP to The picking up of relay 2SA (which picks up a little later than relay VP) closes an energizing circuit for relay E which extends from (-1-), front contact 90 of relay 2SA, conductor |3, back contacts 3| and 32 of relays 2V and IV respectively, front contact 33 of relay VP, conductor |4 and winding of relay E to The picking up of relay E opens the energizing circuit of relay PC at back contact 38, relay PC drops and opens the primary control line circuit to mark the end of the conditioning on period and the beginning of the rst off period.

This drops relays F, FP yand ZFP in the control oice. Relays F3, IF3 and PC3 at the repeater station are de-energized, the dropping vof relay P03 de-energizing the secondary control line vcire` cuit which is effective to drop relays F4 .and kFP1 at the eld station. Relay FN3 is likewise dee energized in response to the de-energization of the secondary control line circuit, but since this relay is ineiective during a control cycle its operation will not further be mentioned during the description of the co-ntrol cycle operation. It need only be mentioned that relay FN3 responds to the impulses applied to the secondary control line circuit.

The dropping of relay ZFP in the control otlice closes a circuit for .picking up relay IV which ,extends from (-1-), front co-ntact l5 of relay SA, back contact 16 of relay 2FP, conductor i5, iront contact 11 of relay VP, back contact 18 of relay 2V and winding of relay IV to Relay IV closes a stick circuit for itself extending from (-1-), front contact 15 of relay SA, conductor I6, front contact 19 and Winding ci relay IV to This stick circuit for relay IV is maintained energized until relay SA is dropped at the vend oi the cycle. It Will be obvious that relays 2V and LV, when picked up, close similar stick circuits for themselves at their front contacts 83 and 84 respectively and it will not be necessary to point out the closure of these stick circuits again during the operation of the system, since they are likewise maintained energized until the end of the cycle.

The picking up of relayIV opens the iirst stick circuit of relay VP at back contact 13, but prior to this a second stick circuit is closed for relay VP which extends from (-1-), front contact 1I of relay SA, back Contact 12 of relay EFP, conductor I1, front contact 86 and Winding of relay VP to The picking up of relay IV de-energizes relay E at back contact 32 and the dropping of relay E picks up relay NC over a circuit extending from (-1-), back contact 38 of relay E, conductor H33, front contact 4! of relay C, back contact 43 of relay 2V, front contact 44 of relay IV, conductor 55, iront contact 51 of relay CD, code jumper 6, NC bus 48 and winding of relay NC to The primary control line circuit is now energized with a impulsev to mark the end of the first off period and the beginning of the rst on period. This circuit extends from battery CB, through back contacts 5I and 53 of relay PC and front contacts 58 and 54 of relay NC, which contacts reverse the connection of the battery applied to the primary control line circuit from that previously pointed out.

The energization of the primary control line circuit effects the picking up of relays F, FP and ZFP in the control office, positioning of the polar contacts of relay F3 at the repeater station to the left, the picking up of relay IF3 and the picking up of relay N03 over an obvious circuit closed at contact 361 of relay F3 in its left hand dotted position. With relay N03 picked up and relay P03 down, the secondary control line circuit is energized with a impulse over a circuit Which includes contacts 35i and,353 of relay PC3 and contacts 356 and 354 of relay NO3 in positions reversed from that previously described.

The .picking up of relay 2FP in the control oiiice drops relay VP because its iirst stick circuit is open at back Contact 13 of relay IV and its second stick circuit is open at back contact 12 of relay 2FP. The droppin-gef relay VP closes a circuit for picking up relay E which extends from (-1-), front contact 98 of relay 2SA, conductor I3, back contact 3l Yof relay 2V, front contact 32 of relay IV, back contact 33 of relay VP, conductor I4 and Winding of relay E to The picking up of relay E de-energizes the above traced circuit for relay NC, which drops and de-energizes the primary control line circuit to mark the end of the rst on period and the beginning of the second oi period. Relays F, FP and 2FP are dropped and relay 2V is picked up over a circuit extending from (-1-), front contact 15 of relay SA, back contact 16 of relay 2FP, conductor I5, back Contact 11 of relay VP, front contact 82 of relay IV and Winding of relay 2V to The picking up of relay 2V deenergizes relay E at open back contact 3I and the dropping of relay E energizes relay NC, which in turn energizes the primary control line circuit to mark the end of the second "oiF period and the beginning of the second on period.

Relays F, FP, and 2F12V .are pi-cked up in response to the energization ofthe primary control line circuit at the beginning of the second on period. Relay VP is picked up over a circuit extending from (-1-), front contact 1I of relay SA, front contact 12 of relay 2FP, conductor I2, front contact 85 of relay 2V and Winding of relay VP to Relay VP again completes and prepares its stick circuits which are believed to be obvious and unnecessary to be pointed out again. The picking up of relay VP energizes relay E over .a circuit extending from (-1-), front contact 90 of relay 2SA, conductor I3, front contacts 3| and 33 of relays 2V and VP respectively, conductor I4 and winding of relay E to The picking up of relay E de-energizes relay NC at back contact 38 and relay NC drops to deenergize the primary control line circuit to mark the end of the second on period and the beginning of the third or clearing out 01T period. Relays F, FP and 2FP are dropped .and relay LV is picked up over a circuit extending from (-1-), front contact 15 of relay SA, back contact 16 of relay ZFP, conductor I5, front contacts 11 and 18 of relays VP and 2V respectively and winding of relay LV to The picking up of relay LV does not change the circuit condition of relay E and it remains up, the PC and NC relays remain down and the primary control line circuit remains de-energized so that relay 2FP remains down for a suiliciently long period to drop relays SA and 2SA for clearing out the circuits. The dropping of relays SA and 2SA de-energize relays E, VP, IV, 2V and LV by the opening of front contacts 90, 1I and 15. 'I'he dropping of relay SA also de-energizes relays CD and C by circuits not shown in the present disclosure.

When relay 2V was picked up during the second oi period as above described, its contact 43 shifted the energizing circuit from conductor 56 to 6I, which extends this circuit through front contact 62 of relay CD, lever SML in its left hand dotted line position (reverse) and NC bus 48 to the Winding of relay NC. This is eiective to apply a,( impulse to the control line circuit during the second on period. It Will be understood that lever SML in its full line (normal) position would energize relay PC instead of relay NC, so that the Vswitch control impulse would be (-1-) instead of i Referring to the eld station illustrated in Fig. 4,. it will be .recalled that the (-1-) and impulses applied to the primary control line circuit are repeated into the secondary control line circuit by the operations of relays PC3 and NC3 respectively at the repeater station. It will be understood that the conditioning and the rst impulses, which were assumed to be (-1-) and because of the connections of jumpers 5 and 6 in the control office, were effective to select the station illustrated in Fig. 4 by maintaining relay S04 in its energized condition.

After the stationis selected the next impulse (second on), which was applied to the secondary control line circuit in response to the impulse applied to the primary control line circuit (because lever SML was assumed to be in its reverse position), positions contact 414 of relay F4 to the left. This closes a circuit for energizing relay SMR4 extending from (CN), winding of relay SMR4, front contact 416 of relay 2V4, front contact 415 of relay S04 and contact 414 of relay F4 in its left hand dotted position to (B This positions contact 450 of relay SMR4 to its left hand dotted position for controlling the operation of the switch machine SM4 for actuating track switch TS4 to its reverse locked position.

It will be apparent that a (-1-) impulse received at the field station of Fig. 4 during the second on period would position contact 4l4 of relay F4 to the right, which would energize relay SMR4 in the opposite direction for positioning Contact 450 to the right for operating the switch machine and track switch to its normal locked position.

It will be understood that relays F2, FP2, F4 and FP4 which follow the impulses in the prifmary and secondary control line circuits remain de-energized at the end of the cycle for dropping relays SA2, S133, SA4, SB4, the stepping relays at the associated stations and relays S02 and S04. Likewise relays S3 and SB3 at the repeater station are dropped during the clearing out period because contacts 365 and 356 of relays NC3 and P03 respectively remain in their dropped away positions for a comparatively long interval of time when the primary control line circuit is deenergized at the end of the cycle.

Indications It will be pointed out in the description which follows how the system is initiated from the field station of Fig. 4 which is-located in the secondary section and how indications Aare transmitted from this station, received at the repeater station and retransmitted to the control office. Although the circuits of a primary eld station (Fig. 2) are shown somewhat in detail it is believed unnecessary to describe the initiation of the system and the transmission of indications from this station, since this portion of the operation of the system is immaterial to an understanding of the present invention and furthermore this operation has been clearly described in the above mentioned prior application 640,062. Also, it is believed that the transmission of indications from the Fig. 4 station by the conditioning of the PB4 and PF4 relays and the reception of these indications by the MB3 and MF3 relays at the repeater station are suiiiciently analogous to the transmission of indications by the PB2 and P132 relays of Fig. 2 and thereception of these indications on the MB and MF relays in the control oice. It will be pointed out in the description which follows how the indications which are received and stored by the MF3 and MB3 relays at the repeater station are transmitted to the control oice.

Automatic start-Assuming the system to be in its normal condition when a change in condition occurs at the eld station illustrated in Fig. 4, relay CH4 is dropped in response to such a change in condition. This closes a circuit for picking up relay L04 which extends from (-1-), back contact 401 of relay FP4, back contact 438 of relay SB4, back contact 453 of relay SA4, upper winding of relay L04 and back contact 454 of relay CII4 to Relay L04 establishes a substitute cir-cuit to at its front contact 455 which bridges back contact 454 of relay CH4.

The secondary indication line circuit is energized, in response to the picking up of relay L04, over a circuit extending from the (-1-) terminal of battery IB1 (Fig. 3), upper winding of relay MF3, back contact 352 or" relay IF3, back contact 396 of relay SB3, secondary indication line IL1, front contact 456 of relay L04, back contact 412 of relay SB4 lower Winding of relay L04, resistance 2R4 and secondary indication line return conductor IR1 to the terminal of battery IBl.

Relay M133 is picked up over the above described circuit and a circuit is closed for picking up relay L03 which extends from (-1-) back contact 310 of relay S3, back contact 388 of relay IF3, front contact 381 of relay MF3, back contact 358 of relay SA3 and upper winding of relay L03 to The picking up of relay L03 energizes the primary indication line circuit over a circuit which may be traced from the (-1-) terminal of battery IB (Fig. 1B), lower winding of relay MB, back contact 9| of relay 2SA, primary indication line conductor IL, back contact 256 of relay L02, indication line conductor IL, front Icontact 356 of relay L03, back contact 312 of relay SB3, back contact 315 of relay FP3, lower winding of relay L03, resistance 2R3 and secondary indication return conductor IR to the terminal of battery IB.

The closing of the primary indication line circuit picks up relay MB which in turn closes a circuit for picking up relay FC at its front contact 34. The pick-up and stick circuits for relay FC have been omitted from the drawings for the sake of simplicity, since the detailed operation of this relay is immaterial for an understanding of the present invention, it being understood that the circuits for controlling relay FC can be the same as disclosed in the above mentioned application Ser. No. 640,062.

Relay NC is energized, in response to the picking up of relay FC, over a circuit extending from (-1-), back contact 38 of relay E, conductor I0, back contact 4| of relay C, front contact 35 of relay FC, NC bus 48 and winding of relay NC to The energization of relay NC applies a conditioning impulse to the primary control line circuit over the previously described circuit including front contacts 5D and 54 of relay NC. It will be assumed that this is a cycle for the transmission of indications alone (not a duplex cycle), so that relay C remains down and relay FC remains picked up for intermittently energizing relay NC by the intermittent operation of contact 38 of relay E as previously described. This provides a series of impulses applied to the primary control line circuit and these impulses eiect the operation of the line relay, the line repeater relays, the stepping relays and relay E in the same manner as described in connection with a control cycle.

It is believed unnecessary to point out in detail how the step-by-step operations in the control oiice and at the field stations are effected, since these operations are the same as already described in connection with a control cycle, with the above mentioned exception that the primary control line circuit is energized with a series of impulses. This positions the polar contacts of relay F3 at the repeater station to the left for each impulse, which picks up relay NO3 to repeat a series of impulses into the secondary control line circuit.

Relays F3, |F3, NO3, S3 and FN3 all operate in response to this series of impulses in the manner previously explained. Since relay L03 is picked up during this indication cycle, relay SA3 is energized in response to the picking up of relay FN3 over a circuit extending from front contact 382 of relay L03, front contact 38d n of relay FN3 and winding of relay SA3 to Relay SA3 being slow acting remains up during the impulsing operations until relay FN3 is dropped at the end of the cycle for a suniciently long period to effect the dropping of relay SA3.

Relay FP3 is picked up during the conditioning on period over a circuit extending from front contact 352 of relay L03, front contact 383 of relay FN3, front contact 385 of relaySA3 and winding of relay FP3 to Since contacts 382 and 385 of relays L03 and SA3 respectively remain up during this cycle, the intermittent operation of relay FN3 is repeated by relay FP3 because of the intermittent opening and closure of front contact 383.

Relay MP3 repeats the operations of relay FP3 by contact 318 intermittently opening the energizing circuit for relay 2FP3 which extends from (-l-), front contact 382 of relay L03 and front contact 318 of relay FP3 to the winding of relay 2FP3. Relay SB3 is picked up during the conditioning on period over a circuit extending from front contact 385 of relay 2FP3, front contact 3S! of relay L03 and winding of relay SB3 to Relay SB3 is stuck up throughout this cycle over a circuit extending from (-l-), front contact 31 of relay SA3, front contact 314 and winding of relay S133 to Relay MB in the control oice, which was picked up to initiate the cycle, remains energized over the above described circuit including the primary indication line circuit, by way ofits lower winding and when relay 2SA is pickedfup during the conditioning on period a stick circuit is completed for relay MB which extends from front contact 66 of relay 2SA, front contact 5B of relay EFP, front contact 64 and upper winding of relay MB to This stick circuit is effective until relay 2FP is dropped during the rst off period, when relay MB is de-energized because the primary indication line circuit is not closed during this period and because the above described stick circuit is open at front contact of relay ZFP.

It will be recalled that relay E is picked' up throughout each off period so that the stick circuit for the upper winding of relay MB is also opened at back contact 65 of relay E. It will thus be seen that relay MB acts as a start relay, after which it is dropped or notV during the first off period as determined by the lrst oit .indication received in the primary indcation line circuit being non-pulse or pulse respectively.

The first conditioning impulse applied to the primary control line circuit eiects the operation of the lineand line repeater relays at the stations in the primary section, but since this is assumed to be a cycle for the transmission of indications alone these impulses are ineffective to select a primary station for controls. Likewise, since theseprimary impulses repeat a series of similar impulses in the secondary line circuit no station in the secondary section is selected for controls.

It will be recalled that relay MF3 at the repeater station Was picked up in response to the energization of the secondary indication line circuit to initiate the cycle. Relay MF3 is maintained energized by current flowing over the secondary indication line circuit in series with its lower Winding until the secondary indication line circuit is opened at the transmitting eld station by the opening of back contact 412 of relay SB4. The closure of front contact 412 is ineffective to close the secondary indication line circuit because the circuit through front contact 513 of relay FP4 is open at front contact 699 of relay PF1. Thus relay MF3 is dropped during the conditioning on period in preparation for its energization or de-energization during succeeding on periods for the reception of on indications from the transmitting eld station.

When relay L03 at the repeater station is picked up in response to the operation of relay MF3, it is maintained energized by way of its lower Winding until relay SA3 is picked up to complete a stick circuit for relay L03 whichv extends from (-1-), front contact 368 of relay L03, front contact 358 of relay SA3 and upper winding of relay L03 to Relay L04 at the transmitting station is stuck up after the operation of relay SA4 over a circuit extending from (-1-), front contact 468'01 relay L04, front contact 453 of relay SA4, upper winding and front contact I of relay L04 to The lock-out oplerations in the primary and secondary sections will be described later.

Transmission of indications from secondary section- Referring to the layout of Fig. 1, it

will be observed that the station registration codes of all stations in the secondary section begin with a As indicated by the note in Fig. l, a symbol refers to the condition of a non-pluse in the indication line circuit and a -lsymbol refers to a pulse in the indication line circuit. It will likewise be noted that the registration codes associated with the stations in the primary section begin with a In the ydescription which follows it will be explained how four digitsof code are received in the control ofce with only three digits of code transmitted from station No. 5 in the secondary section. Referring to the upper left hand portion of the typical indication code table of Fig. 5, it will be assumed that code No. 5, which is associated with station No. 5, is received in the control oice in response to station No. 5 initiating an indication cycle. Referring to the lower right hand section of Fig. 5 it will be observed that station No. 5 transmits only two .digits of station registration code With the third digit (2nd 01T) being used for the transmission of an indication from the registered station. It will also be observed that the second and third digits of the No. 5 station registration code are transmitted in the first 01T and first on periods respectively and that these digitsv are received in the control office in the first on and the second off periods respectively. As will be later pointed out the rst digit of the No. 5

station registration code is not transmitted but is registered during the rst ofi period of the cycle to complete the code which is associated with station No. 5.

The same discussion applies to other stations in the secondary section, that is, since the code for each of these stations begins with a it is not transmitted but in effect it is registered in the control oiiice during the rst off period. T'his is possible since for any given size of registration unit, one-half of the total registration codes necessarily start off with a or non-pulse, and whether this non-pulse is the result of a deliberate choice or the result or the inability of the eld station to pulse the indication circuit on the first half-step is immaterial in-so-far as the correct registration of the station in the oilice is concerned.

In other Words, the lrst code element for each of the field stations in the secondary indication line circuit requires a non-pulse and this nonpulse is represented in the code table of Fig.

showing the codes transmitted from the repeater station as indicated by the minuses for the rst off period. As the repeater station has not received a pulse element for distant field stations, it then transmits for such ofi period a nonpulse code element and this non-pulse code element is transmitted because of the open condition of contact 39| of relay MF3 in the same sense that a non-pulse is transmitted by any of the relays PF for the eld stations shown in Figs. 2 and 4.

To put ,it still another Way, the non-pulse or the first code element for each of the neld stations in the secondary indication line circuit, requires no operation on the part of the eld station or on the part 0i the repeater station. But the repeater station is effective to produce a non-pulse condition on this rst time period which is allotted on the primary indication line circuit for the existence of a code element condition, and on the same time period, a code element is transmitted to the repeater station over the secondary indication line circuit by a pulse or an non-pulse condition which can be stored for transmission on the second time period for the primary indication line circuit. This arrangement provides, that although the actual effect of a distant eld station which is repeated through a repeater station is delayed a half-step, such delay does not result in the requirement of added steps by reason of the manner in which the station selecting codes are arbitrarily chosen in accordance with the principles of the present invention.

From the above it follows that for any given size of registration unit one-fourth of the total registration codes start ofi with tWo-non-pulses and these can be used in a succeedingthird section with no loss of capacity. likewise oneeighth of the total registration codes (in a system of the proper size) start off with three nonpulses and these codes can be used in a succeeding fourth section with no loss of capacity.

Thus, it is seen that for each of the non-pulse code elements for the stations beyond a repeater station, a non-pulse code element condition is set up in the indication line circuit extending from such repeater station by that particular repeater station. For example, if there are three repeater stations, the first repeater station from the control oiiice will condition the primary indication line circuit with three non-pulse conditions; the second repeater station Will condition the second indication line circuit with two non-pulse conditions and the third repeater station will condition the third indication line circuit With one non-pulse condition. These nonpulse code elements occur automatically and the corresponding step periods at the eld station transmitting can be used to transmit the code elements from that station on which there is a possibility of a pulse condition occurring and When such pulse code elements do occur they are relayed on through the repeater stations so as to arrive at the control oice upon the right halfstep period because of the intervening non-pulse code elements having; been automatically impressed upon the primary indication line circuit.

During an indication cycle, indications are transmitted from a secondary field station, illustrated in Fig. 4 for example, to the repeater station illustrated in Fig. 3 by the conditioning of the secondary indication line circuit. Relays LO4 and S134 remain picked up at the transmitting field station throughout the indication cyle so that the circuit of the secondary indication line, including front contact 412 of relay SBl, can be opened or closed during both the on and oif periods as selected by contact 413 of relay FP4 in accordance with the closed or open conditions of contacts 499 and 49| of relays PF4 and PB4 respectively.

During each off period in the series of impulses the (-1-) terminal of indication battery IB1 (Fig. 3) is connected to secondary indication line conductor ILl through the upper Winding of relay MB3 and current flow in the secondary indication line circuit is dependent upon front contact 49| of relay PB4 being closed. More specically, relay PB4 is the code transmitter for the off periods of the impulses in the secondary line circuit. Assuming jumper 480 at the transmitting secondary station (illustrated in Fig. 4) to be connected to (-i-) as shown, relay PBl is picked up during the conditioning on period over a circuit extending from jumper 48D, back contacts 485 and 486 of relays IV4 and 2V4 respectively, front contact 488 of relay FP1, Winding of relay PB4 and front contact 489 of relay L04 to The picking up of relay P134 provides one of a choice of two off indications.

When relay FP4 is dropped during the rst off period, relay PB4 is stuck up over a circuit extending from front contact 490 of relay PE4, back contact 488 of relay FP4, winding of relay PB4 and front contact 489 of relay LO4 to When relay Fl?4 is picked up during the first on period the above described stick circuit is opened and the energization of relay PB4 is dependent upon a circuit extending through front Contact 485 of relay IV4 for the second off indication, to contact 492 of relay T4, which being open illustrates the alternate choice of an oit indication. Relay PB4 will be de-energized to transmit this alternate choice off indication,

With relay PB4 picked up during the conditioning on period and stuck up throughout the rst oit period as above described, the secondary indication line circuit is closed as will be presently pointed out. This indication line circuit was opened .during the conditioning on period when relay SB4 opened its back contact 412.

The lock-out period for maintaining relay LO4 energized extends from the time of the picking up of relay FP4 and the consequent opening of its back contact 401 until the picking up of relay SA4 and the consequent closing of its front contact 453, during which period relay L04 isv dependent for its energization on line current received from battery IB1, at the repeater station, through its` lower winding. In the event that some other station superior to the station of Fig. 4 (in the event that the Fig. 4 station is not the station nearest the repeater station) opens the secondary indication line circuit during this lock-out period, then of course relay L04 ls dropped and it cannot be picked up again until the start of another cycle. With relay L04 maintained picked up during the lock-out period, then when relay SA4 closes its front contact 453, relay L04 is stuck up over a` circuit including its upper winding and its front contacts 455 and 468 in series with front Contact 453 of relay SA4. Thus relay L04 is maintained picked up until relay SA4 dro-ps at the end of the cycle.

During each on period the secondary indication line circuit remains open or is closed depending upon contact 499 of relay PF4. For example assuming that code jumper 482 is connected to as shown in Fig. 4, relay PF4 is picked up during the rst ofi period over a circuit exten-ding from (-1-), jumper 482, back contact 494 of relay 2V4, front contact 496 of relay VP4, back contact 491 of relay FP4, winding of relay PF4 and front contact 489 of relay L04 to When relay FP4 is picked up during the rst on period, relay PF4 is stuck up over a` circuit extending from front contact 498 of relay PF4, front contact 491 of relay FP4, winding of relay PF4 and front contact 489 of relay L04 to The above illustrates one choice of an on indication whereby relay PF4 is picked up. The other choice on indication is effected by the de-energization of the circuit including the Winding of relay PF4 and back contact 491 of relay FP4. The second choice on indication de-energizes relay PF4 in the second 01T period so that relay PF4 is down throughout the second on period.

It will now be explained how the conditioning of relays PB4 and PF4 eiect the closing and the opening of the secondary indication line circuit for transmitting indications to the repeater station where they are received, stored and retransmitted to the office.

From the above discussion of the conditionlng of the PB4 and PF4 relays it will be observed that relay FP4 is positioned during an off period in accordance with the indication it is to transmit in the next on period, while relay PB4 is positioned during an on period in accordance with the indication it is to transmit in the next off period. Thus on each step taken by the step-by-step mechanism at the eld station, relays PF4 and PB4 govern the secondary indication line circuit.

As Will be later pointed out an indication code which is started from the station in the secondary section during the iirst off period is not received in the control oice until the next or rst on period. Therefore the code digit 2+, illustrated in the lower right hand section of Fig. 5 as being the rst code transmitted from station No. 5, is received in the control oice as the second code digit for station No. 5 as is indicated in the upper left hand portion of the indication code table of Fig. 5. Therefore code jumper 459 conditions relay PB4 to transmit the second digit of the code associated with station No. 5. It'will be later explained how the first digit of the-code,

that is a non-pulse, registers itself in the control-cnice to complete the station registration code.

It will be recalled that the secondary indication line circuit was opened during the conditioning on period by the picking up of relay S134 and the consequent opening of its back contact 412. The dropping of relay 2FP3 at the repeater station during the first off period permits current to flow in the secondary indication line circuit because relay PB4 is picked up throughout this first 01T period. The circuit for this current ow may be traced from the (-1-) terminal of battery IB1, upper winding of relay M153, back Contact 391 of relay FN3, back contact 3940i relay FP3, back contact 392 oi relay 2FP3, front contact 399 of relay L03, front contact 396 of relay SB3, secondary indication line conductor IL1, front contacts 456 and 412 of relays L04 and SB4 respectively, back contact 413 of relay FP4, front contact 49H of relay PB4, resistances IR4 and 2R4 in series and indication return conductor IR1 to the terminal of battery IBl.

This energization of the secondary indication line picks up relay MB3 to register the first digit of the code transmitted from station No. 5 which is actually the second digit of the station reg-v istration code. Relay MB3 is maintained picked up by current in the secondary indication line circuit until relay lF3 picks up to close a stick circuit for relay MB3 which extends from (-l-l, front contact 36| of relay BB3, front Contact 390 of relay |F3, front contact 364 and lower winding of relay M133 to Relay MB3 is thus stuck up throughout the on period, following the oir period during which it was picked up. Relay MB3 is dropped when relay IF3 drops and opens the above described stick circuit at front contact 390.

The picking up of relay FN3 at the repeater station at the beginning of the rst on period opens the secondary indication line circuit at back Contact 391. 'Ihis de-energizes the secondary indication line circuit and when relay 2FP31is-pieked up during the rst on period the secondary indication line circuit is again energized because relay PF4 at the eld station is picked up.

' The "energizing circuit for the secondary indication line extends from the (-1-) terminal of battery IBI, upper winding of relay MF3, front contact 398 of relay FN3, front contact 393 of relay FPS, front contact 392 of relay 2FP3, front contact 399 of relay L03, front contact 395 of relay SBS, secondary indication line conductor IL1, front contacts 456 and 412 of relays L04 and SB4 respectively, front contact 413 of relay FP4, front contact 499 of relay PF4, resistances |R4 and 2R4 in series and indication return conductor IR.l to the terminal of battery IBI. This eiects the picking up of relay MF3, which relay is maintained energized through its upper winding until relay IF3 drops to complete the stick circuit extending from front contact 36| oi relay SB3, back contact 369 of relay EFS, front contact 363 and` lower winding of relay MF3 to It will thus be observed that relay MF3 when picked up during an on period is stuck up throughout the following off period.

The dropping of relay 2FP3 during the second 01T period fails toclose the secondary indication line circuit because of open front contact 49! of relay'PBl. When relay 2FP3 is picked up during the second on period the secondary indication line circuit Ais not closed because of open front-contact 499fof relay PF4, which relay is down during this on period. It is believed unnecessary to trace the circuit for the secondary indication line since the energized and de-energized conditions of this line have been pointed out in the above typical examples.

Since the secondary indication line circuit is not energized during the second off period, relay MB3 is dropped during this period when relay IF3 drops and opens its front contact 360. Relay MF3 which was picked up during the rst on,period is dropped at the end of the second ofi period when relay IF3 picks up and opens back contact 360.

From the above it will be observed that relay MB3 is selectively responsive during the ofi periods to the energization and de-energization of the secondary indication line circuit for receiving either one of a choice ci two distinctive indications, with the selected choicemaintained throughout the following on period of relay MB3 either being up or down throughout this on period. Similarly, relay MF3 is selectively responsive during each on period in accordance with one or another choice of two indications transmitted during each on period, with relay Ml.3 remaining up or down throughout the following off period to register the selected indication which was transmitted and received by this relay.

It will be recalled that relay PB4 was dropped during the first on period after transmitting the first off code digit which was a -1- (pulse). Relay PB4 is then in condition to be picked up to transmit an indication during the second off period in accordance with the condition of track relay T4 for example. With relay T4 energized, as illustrated in Fig. 4, relay PB4 will not be picked up during the rst on period. This effects the transmission of a (non-pulse) code digit during the second 01T period. On the other hand, if relay T4 is down, then a circuit is completed through back Contact 492 for picking up relay PB4 during the first on period for transmitting a (pulse) code digit during the second off period. This is illustrated in the fifth column of the lower right hand section of Fig. 5 by the code digit associated with the second off period being indicated 4.-]- or 0- which are the codes transmitted by relay T4 being down or up respectively.

Transmission 0f indications to control oice.- The above explantion points out how three code digits (see lower right hand section of Fig. 5 table) are transmitted from a secondary eld station during the rst off, rst on and second off periods and received at the repeater station during the corresponding periods. It will now be eX- plained how these three code digits which Were received and stored on relays MIB3 and MF3 are retransmitted over the primary indication line circuit during the rst on, second oi and second on periods respectively.

It will be recalled that the primary indication line circuit was energized with a start pulse by the picking up of relay L03 to initiate the cycle. The primary indication line circuit is de-energized during the conditioning on period when relay Fl?3 at the repeater station picks up and opens its back contact 315. The closure of front contact 312 of relay SB-'f does not energize the primary indication line circuit because of open front contact 399 of relay MB3.

During the rst off period, battery IB (see Fig. 1B) is connected to the primary indication line circuit through the lower winding of relay MB and current flow in the primary indication line circuit is dependent upon front contact 39| of relay MP3. It will be recalled that relay MF3 receives the on indications from the station in the secondary section and since the rst on indication has not yet been transmitted to the repeater station, relay MF3 is down during the first off period and therefore the primary indication line closure cannot be completed. Likewise relay MB3 which receives off indications from the transmitting station in the secondary section transmits these off indications to the office during the succeeding on periods. Therefore the control ofiice can not complete the closure of the primary indication line circuit during an indication cycle when indications are being transmitted from a station in the secondary section. This means that a (non-pulse) will always be received during the rst off period in the control ofce when a station in the secondary section is transmitting.

Relay MB in the control office is therefore the code receiver for on indications transmitted from the secondary section and relay MF is the code receiver for off indications transmitted from the secondary section. Relay MB is the code receiver for 01T indications transmitted from the primary section and relay MF is the code receiver for on indications transmitted from the primary section. Since these indications transmitted from the primary section effect the operation of relay MB and MF in the same manner as the transmission of indications in the secondary section effect the conditioning of relay MB3 and MF3 as previously described, it is believed unnecessary to point out how indications are transmitted from a station in the primary section.

Referring back to the picking up of lock-out relay L03 at the repeater station, it will be understood that the lock-out period for maintaining relay L03 energized extends from the time of the picking up of relay IF3 and the consequent opening of its back contact 388 until the picking up of relay SA3 and the consequent closure of its front contact 358, during which period relay L03 is dependent for its energization on line current received from battery IB in the control oice and through its lower winding. In the event that some station in the primary section (which is superior to the repeater station) opens the primary indication line circuit during this lockout period, then relay LO3 is dropped and it cannot be picked up again until the start of another cycle. With relay L03 maintained picked up during the lock-out period, then when relay SA3 closes its front contact 358, relay L03 is stuck up over a circuit including its upper winding and its front contact 368 in series with front contact 358 of relay SAS. Thus relay LO3 is maintained picked up until relay SA3 drops at the end of the cycle.

It will be recalled that the lock-out period for stations in the secondary section extends from the time that relay FP4 is picked up until the time that relay SA4 is picked up. Since this period overlaps the lock-out period of the repeater station it Will be obvious that a station in the secondary section which initiates the system into an indication cycle can be ruled out during its lock` out period in the event that a station in the primary section takes the line and opens the primary indication line circuit back towards the repeater station.

Recalling that the primary indication line circuit cannot be pulsed during the rst off period by a station in the secondary section, this nonpulse or code digit effects the dropping of relay MB during the first 01T period, which relay was picked up to initiate the system. With relay MB down the rst code digit, which is is executed during the rst on period with iront contact 8| of relay FP closed. This executing circuit extends from (B back contact 91' of relay MB, front contact 8l of relay FP, conductor I8, front contact 31 of relay FC, back contact 55 of relay 2V, front contact 58 of relay IV, conductor and upper winding of relay IPB to (B-). Since (B-) is connnected to both terminals of the upper winding of relay IPB this relay remains down to register the first code digit as being or non-pulse. Since it was previously pointed out that no station in the secondary section can transmit a or pulse code digit which is received in the control oilice during the iirst oli period, it will be evident that no station in the secondary section can pick up relay IPB.

The second code digit is received in the control oce during the rst on period and is the code digit which was transmitted 'from the field station in the secondary section during the iirst on period. It will be recalled that this code digit kpicked up relay MB3 at the repeater station and maintained it picked up throughout the rst on period. The primary indication line circuit is therefore energized during the rst on period when relay 2FP picks up and closes its front contact 92 and until relay NC drops and opens its front contact 20. This is because relay MB3 was maintained in its picked up .position throughout the first on period so that the primary indication line circuit is energized overa circuit extending from the terminal of battery IB, lower winding of relay MF, back contact 22 of relay PC, front contact 29 of relay NC, front contact 93 of relay FP, front contact 92 of relay 2FP, front contact 99 of relay FC, front contact 9i of relay 2SA, indication line conductor IL, back contact 256 of relay L02, indication line conductor IL, front contact 356 of relay L03, front contact 312 of relay SB3, front contact .313 of relay IF3, front contact 399 of relay MB3, resistance units I R3 and 2R3 in series and indication return conductor IR to the terminal of battery IB.

Relay MF is picked up over the above described circuit and is held up by current flowing over the primary indication line circuit until relay E is picked up to mark the beginning of the second off period, when a stick circuit is closed for `relay MF which extends from (-1-), front contact 6B of relay 2SA, front contact 65 of relay E, front contact 63 and upper winding of relay MF to When relay E drops to mark the end of the second olf period the stick circuit for relay MF is maintained complete vat back Contact 69 of relay 4ZFP so that relay MF is not dropped until relay FP picks up during the second on period while relay E is down. Therefore relay MF is maintained picked up throughout the second off period to Vexecute the second code digit by means of `an executing circuit which extends from (B+), front contaet'96 of relay MF, back Contact 86 of relay E?, conductor 9, front Contact 81 of relay FC, back contact 88 of relay VP, front contact 89 of relay IV, conductor 49 and upper winding of relay IPF to (B-).

Relay IPF is picked up, and stuck up until the end of the cycle over its stick circuit which extends irom (-l-), fron-t contact `59 of relay SA, conductor `112, front contact 5.2 and lower winding'of relay EPF to 'Ihe'primary indication `linelcircuit is cle-energized attheend of the rst on period by the dropping of relay NC and the consequent opening of its front contact 2U.

The third code digit to be received in the control oilice is (pulse) in the primary indication line circuit. This is 'because when relay 2FP drops during the second ofi period to close its back contact 92, a circuit is closed for energizing the primary indication line circuit which may be traced from the (-1-) terminal of battery IB, lower winding of relay MB, back contacts 23 and 2| of relays PC and NC respectively, back contacts 94 and 92 of relays FP and EFP respectively, front ccntacts 9S and BI of relays FC and 2SA respectively, primary indication line conductor IL, back Contact 25% of relay L02, indication line conductor IL, front contact 356 of relay L03, front contact 312 of relay SBS, back contact 313 of relay IFB, front Contact SSI of relay MF3, resistance units I R3 and 2R3 in series and primary indication return conductor IR to the terminal of battery IB. The primary indication line circuit is cle-energized when relay NC picks up and opens the above described circuit at its back contact 2 I.

When the primary indication line circuit is energized during the second off period, relay MB is picked up and maintained energized by way of its lower winding until its stick circuit is closed by the closure of back contact 65 when relay E drops to mark the end of the second oil period. The picking up of relay 2FP closes a substitute stick circuit for relay MB at its iront contact 6I! which is maintained after the picking up of relay E and until relay ZFP is dropped during the third oir period.

This indication which was received on relay MB in the second 01T period is executed during the second on period by means of a circuit extending from (B+), front contact 91 of relay MB, front contact 8| of relay FP, conductor I8, front contact 31 of relay FC, front contact 55 of relayZV, conductor 30 and upper winding of relay EPB to (B-). Relay 2PB is picked up and closes an obvious stick circuit for itself by way of its lower winding to (-1-) on conductor 42.

Since the three code digits above described comprise the station registration code, station relay 5ST (which corresponds to station No. 5) is picked up when relay LV is picked up during the third 01T period over a circuit extending from (-i-), front contact 3E of relay LV, conductor 26, back contact 24 of relay IPB, front contact 25 of relay IPF, front contact 28 of relay EPB and winding of relay 5ST to The transmission of the fourth code digit does not pulse the primary indication line circuit, since it was assumed that contact 492 of relay T4 of Fig. 4 is open. It will be recalled that this fourth code digit was transmitted from the secondary eld station as a (non-pulse) because relay PB4 was not up during the irst on period, which resulted in relay MB3 not being picked up during the second oir period. Since this fourth code digit is retransmitted to the control oice during the secondfon period and since relay MB3 is not picked up during this period, it will be obvious that the primary indication line circuit cannot be energized when the control oce connects relay MF and battery IB in the primary indication line circuit during the second on period.

Therefore relay MF'will remain down in respense to this fourth code digit and when this code digit is executed it effects the positioning of -relay IRF to the right by means of a circuit extending from (B back contact St" of relay MF, back contact 86 of relay FP, conductor 9, front contact 81 of relay FC, front contact 88 of relay VP, front contact 98 of relay 2V, conductor 3S, iront contact I9 of relay 5ST and winding of relay IRF to (CN). Current iiow in this circuit positions the polar contact of relay IRF to the right for displaying the proper indication that track relay T4 is picked up. It will be obvious that the alternate -fourth code digit is transmitted when track relay T4 is down, which finally results in the picking up of relay MF during the second on period so that it is up during the third off period to apply (B+) over the above described circuit by way of its front con- 'tact 95 for positioning the polar contact oi relay IRF to the left.

The above illustrates how the off indications (choice of two) which start from a eld station in the secondary section during one off period are received in the control oflice during the succeeding on period and executed during the succeeding oi period. Likewise, examples are given of the manner in which on indications (choice of two) which leave a eld station in the secondary section during an on period are received in the control office during the succeeding off period and executed during the next succeeding on period.

It is believed that the above examples are sufiicient to indicate how these code digits are transmitted, stored, retransmitted and executed for additional steps of a cycle and it will be understood that as many such code digits may be provided as desired by increasing the number of steps taken by the stepping relay banks.

At the end of the indication cycle the last off period is effective to de-energize the SA and the 2SA relays as well as the VP, the E, stepping relays and the CD and C relays in the same manner previously described in connection with a control cycle. Relay FC in the control oflice, which is maintained picked up during an indication cycle, is likewise de-energized at the end of the cycle by the dropping of relay SA.

Lock-out.-Assuming that a eld station in the secondary section has new indications to transmit to the control oilice when the system is in its condition of rest, the field station thus involved closes the secondary indication line circuit and this results in the picking up of relay MF3, followed by the picking up of relay L03 at the repeater station. The picking up of relay L03 at the repeater station closes the primary indication line circuit which picks up relay MB in the control oice to initiate the operation of the system.

As a result of this eld start the control oice applies a conditioning impulse to the primary control line circuit, which impulse is repeated into the secondary control line circuit. The picking up of relay IF3 in the primary control line circuit opens the pick-up circuit of relay L03 at back contact 388 and leaves relay L03 stuck up by line energy from the control office over the primary indication line circuit.

In this condition relay L03 at the repeater station is subject to being locked out or overruled by any eld station in the primary section in exactly the same manner as the lock-out between individual iield stations of the primary section. In the event that relay L03 of the repeater station is locked out by a superior iield station (one nearer the control oflice) its release (since relay IF3 is now picked up during the conditioning period) will immediately remove energy from the secondary indication line circuit and thus release any lock-out relay in the secondary section that happens to be picked up.

However if relay L03 at the repeater station is not overruled by a superior station it will remain stuck up during the lock-out period by line energy from the control oflice until its local stick circuit is established by relay SA3 closing its iront contact 358. In case relay L03 of the repeater station is not overruled by a superior station in the primary section it will maintain energy to the secondary indication line circuit until after the lock-out has been eiected between the individual stations of the secondary section. Thereafter energy to the secondary indication line circuit is applied through the pick-up coils of the MB3 and MF3 relays and through the pulsing contacts of the FN3, FP3 and 2FP3 relays, through front contact 390 oi1 relay L03 and front contact 396 of relay SB3.

Indication Zine circuit prccharging-From the foregoing description it will be observed that the indication receiving relays MF3 and MB3 at the repeater station and the indication receiving relays MF and MB in the control office are connected in the secondary indication line circuit and the primary indication line circuit respectively in such a manner that they are controlled in accordance with the open or closed condition of transmitting contacts at the secondary transmitting station and at the repeater station respectively. With such an arrangement it happens that the sequence of events is such that the distributed capacity of the indication line circuits becomes discharged so that the application of energy to these circuits may result in a temporary surge of current which is conveniently termed the charging current. This charging current ilows irrespective of whether the line circuit is open or closed at the location from which an indication is to be received.

It has been found in some instances that the charging current that ows into an open circuited indication line reaches a peak value which is considerably greater than the current that normally flows under the stable conductive condition of the line circuit and that this charging current surge lasts for an appreciable length of time. Under these conditions the message receiving relay in the indication line circuit, for the purpose of detecting the conductive condition of the line, may be undesirably picked up by the charging current when such relay was supposed to remain down in accordance with the open circuit condition of the line.

During an indication cycle the secondary indication line circuit is impulsed and, in accordance with the contact arrangement comprising contacts 392, 393 and 394 of relays 2FP3 and FP3 of Fig. 3, a precharge is applied to the secondary indication line circuit.

During the transfer from one period to another, that is from an on period to an oir period or vice versa, there is an interval of time during which the secondary indication line circuit is not energized from battery l'B1 and during which time the distributed capacity of the secondary indication line circuit may become discharged by reason of the closed condition of one of its controlling contacts at the field station. This is because the field station apparatus is not permitted to change the condition of the secondary indication line circuit until after this line circuit is opened at the repeater station, which is necessary to provide that the message receiving 

